It seems that, to an extent, Geiger was to the Marine Corps what Wolfram v. Richthofen was to the Luftwaffe. Richthofen was originally against the stuka concept but became one of its finest users of the Luftwaffe in the ground attack role. He was able to work closely with the army commanders he was to support such as Manstein. He initiated some of the first forward air controllers and was able to hone air/ground cooperation to the fullest, especially during Barbarossa and the Eastern Campaign. It was not unusual for Richthofen (an equivilant to a corps commander) to personally work as a FAC in critical situations. While Geiger made sure his airmen understood the jobs of the ground and naval forces they'd be working with, Richthofen made sure that the ground commanders understood the capabilities and limitations of the Luftwaffe as well. This system heavily relied on the mutual respect, cooperation and understanding of the ground and air commanders. This cooperation and mutual understanding was something that the Western Allies took some time to learn. It was too easy for inter-service rivalries to get in the way. Fortunately, the USA had General Pete Quesada who was able to work effectively with the ground components. The RAF took somewhat longer to get up to speed. However, it was Richthofen who was instrumental in installing liason personnel in Heer units down to division level so that those commanders could get the maximum effect from the air assets assigned to assist them. This system worked well until the demands on the Luftwaffe became so great that the system collapsed later in the war due to lack of bombers and fuel. So while the Germans had unity of command, usually under the tactical command of the Heer, it was Ricthofen who helped facilitate the necessary cooperation that was essential to get the most out of a combination of air and ground forces. By the way, much of Richthofen's ideas came out of the Spanish Civil War and were developed by his subordinate, Adolph Galland, who's after-action reports essentially were the first "book" on air/ground tactics and cooperation.